Fig. 47.—Amphistomum subclavatum of the frog.
Fig. 48.—Polystomum integerrimum.
Independently of these worms, the vegetable-feeders afford lodging to some which are not their own.
We have found in bats two tæniæ, both incompletely developed, and occupying the digestive tube. One has a rostellum without hooks, like the tæniæ of the vegetable-feeders, the other has hooks like those of the carnivora. These cestode parasites are observed to be of two principal forms; the first vesicular, like the finger of a glove partly drawn inwards. They are always lodged in the midst of the flesh, or in a closed organ in the middle of a cyst; under this form the cestode worm is harboured by a host which is to serve as a vehicle to introduce him into his final host. He is a parasite on a journey; he is always agamous, and usually bears the name of cysticercus ([Fig. 49]). As to the second form, it is like a ribbon; it attains a great length, always occupies the intestine, attains its complete and sexual development, and lays an innumerable quantity of eggs which are disseminated with the evacuations.
Fig. 49.—Cysticercus; a, upper part of the vesicle; b, place where the vesicle is about to separate; c, neck of the worm; d, the head, showing the suckers and the crown of hooks.